Three voltage amplifiers are in cascade as shown in Figure P12.8 with various amplification factors. The 180 degree phase shift for negative feedback actually occurs in the basic amplifier itself.

(a) Determine the value of \(\beta\) such that the closed-loop voltage gain is \(A_{v f}=V_{o} / V_{s}=-120\).

(b) Using the results of part (a), determine the percent change in \(A_{v f}\) if each individual amplifier gain decreases by 10 percent.

Transcribed Image Text:

Figure P12.8 VE A =-10 A2=-15 A3=-20